Netty4.0学习笔记系列之三：构建简单的http服务

本文主要介绍如何通过Netty构建一个简单的http服务。

想要实现的目的是：

1、Client向Server发送http请求。

2、Server端对http请求进行解析。

3、Server端向client发送http响应。

4、Client对http响应进行解析。

在该实例中，会涉及到http请求的编码、解码，http响应的编码、解码，幸运的是，Netty已经为我们提供了这些工具，整个实例的逻辑图如下所示：

其中红色框中的4个类是Netty提供的，它们其实也是一种Handler，其中Encoder继承自ChannelOutboundHandler，Decoder继承自ChannelInboundHandler，它们的作用是：

1、HttpRequestEncoder：对httpRequest进行编码。

2、HttpRequestDecoder：把流数据解析为httpRequest。

3、HttpResponsetEncoder：对httpResponset进行编码。

4、HttpResponseEncoder：把流数据解析为httpResponse。

该实例涉及到的类有5个：HttpServer HttpServerInboundHandler HttpClient HttpClientInboundHandler ByteBufToBytes

1、HttpServer 启动http服务器

package com.guowl.testhttpprotocol;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;

public class HttpServer {
	public void start(int port) throws Exception {
		EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
		EventLoopGroup workerGroup = new NioEventLoopGroup();
		try {
			ServerBootstrap b = new ServerBootstrap(); // (2)
			b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class) // (3)
					.childHandler(new ChannelInitializer<SocketChannel>() { // (4)
								@Override
								public void initChannel(SocketChannel ch) throws Exception {
									// server端发送的是httpResponse，所以要使用HttpResponseEncoder进行编码
									ch.pipeline().addLast(new HttpResponseEncoder());
									// server端接收到的是httpRequest，所以要使用HttpRequestDecoder进行解码
									ch.pipeline().addLast(new HttpRequestDecoder());
									ch.pipeline().addLast(new HttpServerInboundHandler());
								}
							}).option(ChannelOption.SO_BACKLOG, 128) // (5)
					.childOption(ChannelOption.SO_KEEPALIVE, true); // (6)

			ChannelFuture f = b.bind(port).sync(); // (7)

			f.channel().closeFuture().sync();
		} finally {
			workerGroup.shutdownGracefully();
			bossGroup.shutdownGracefully();
		}
	}

	public static void main(String[] args) throws Exception {
		HttpServer server = new HttpServer();
		server.start(8000);
	}
}

2、HttpServerInboundHandler 解析客户端的请求，并进行响应

package com.guowl.testhttpprotocol;

import static io.netty.handler.codec.http.HttpHeaders.Names.CONNECTION;
import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_LENGTH;
import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
import static io.netty.handler.codec.http.HttpResponseStatus.OK;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpContent;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpHeaders.Values;
import io.netty.handler.codec.http.HttpRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.guowl.utils.ByteBufToBytes;

public class HttpServerInboundHandler extends ChannelInboundHandlerAdapter {
	private static Logger	logger	= LoggerFactory.getLogger(HttpServerInboundHandler.class);
	private ByteBufToBytes reader;

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		if (msg instanceof HttpRequest) {
			HttpRequest request = (HttpRequest) msg;
			System.out.println("messageType:" + request.headers().get("messageType"));
			System.out.println("businessType:" + request.headers().get("businessType"));
			if (HttpHeaders.isContentLengthSet(request)) {
				reader = new ByteBufToBytes((int) HttpHeaders.getContentLength(request));
			}
		}

		if (msg instanceof HttpContent) {
			HttpContent httpContent = (HttpContent) msg;
			ByteBuf content = httpContent.content();
			reader.reading(content);
			content.release();

			if (reader.isEnd()) {
				String resultStr = new String(reader.readFull());
				System.out.println("Client said:" + resultStr);

				FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, Unpooled.wrappedBuffer("I am ok"
						.getBytes()));
				response.headers().set(CONTENT_TYPE, "text/plain");
				response.headers().set(CONTENT_LENGTH, response.content().readableBytes());
				response.headers().set(CONNECTION, Values.KEEP_ALIVE);
				ctx.write(response);
				ctx.flush();
			}
		}
	}

	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		logger.info("HttpServerInboundHandler.channelReadComplete");
		ctx.flush();
	}

}

3、HttpClient 向服务器发送请求

package com.guowl.testhttpprotocol;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.DefaultFullHttpRequest;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpMethod;
import io.netty.handler.codec.http.HttpRequestEncoder;
import io.netty.handler.codec.http.HttpResponseDecoder;
import io.netty.handler.codec.http.HttpVersion;

import java.net.URI;

public class HttpClient {
	public void connect(String host, int port) throws Exception {
		EventLoopGroup workerGroup = new NioEventLoopGroup();

		try {
			Bootstrap b = new Bootstrap(); // (1)
			b.group(workerGroup); // (2)
			b.channel(NioSocketChannel.class); // (3)
			b.option(ChannelOption.SO_KEEPALIVE, true); // (4)
			b.handler(new ChannelInitializer<SocketChannel>() {
				@Override
				public void initChannel(SocketChannel ch) throws Exception {
					// 客户端接收到的是httpResponse响应，所以要使用HttpResponseDecoder进行解码
					ch.pipeline().addLast(new HttpResponseDecoder());
					// 客户端发送的是httprequest，所以要使用HttpRequestEncoder进行编码
					ch.pipeline().addLast(new HttpRequestEncoder());
					ch.pipeline().addLast(new HttpClientInboundHandler());
				}
			});

			// Start the client.
			ChannelFuture f = b.connect(host, port).sync(); // (5)

			URI uri = new URI("http://127.0.0.1:8000");
			String msg = "Are you ok?";
			DefaultFullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST,
					uri.toASCIIString(), Unpooled.wrappedBuffer(msg.getBytes()));

			// 构建http请求
			request.headers().set(HttpHeaders.Names.HOST, host);
			request.headers().set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
			request.headers().set(HttpHeaders.Names.CONTENT_LENGTH, request.content().readableBytes());
			request.headers().set("messageType", "normal");
			request.headers().set("businessType", "testServerState");
			// 发送http请求
			f.channel().write(request);
			f.channel().flush();
			f.channel().closeFuture().sync();
		} finally {
			workerGroup.shutdownGracefully();
		}

	}

	public static void main(String[] args) throws Exception {
		HttpClient client = new HttpClient();
		client.connect("127.0.0.1", 8000);
	}
}

4、HttpClientInboundHandler 对服务器的响应进行读取

package com.guowl.testhttpprotocol;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.http.HttpContent;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpResponse;

import com.guowl.utils.ByteBufToBytes;

public class HttpClientInboundHandler extends ChannelInboundHandlerAdapter {
	private ByteBufToBytes reader;

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		if (msg instanceof HttpResponse) {
			HttpResponse response = (HttpResponse) msg;
			System.out.println("CONTENT_TYPE:" + response.headers().get(HttpHeaders.Names.CONTENT_TYPE));
			if (HttpHeaders.isContentLengthSet(response)) {
				reader = new ByteBufToBytes((int) HttpHeaders.getContentLength(response));
			}
		}

		if (msg instanceof HttpContent) {
			HttpContent httpContent = (HttpContent) msg;
			ByteBuf content = httpContent.content();
			reader.reading(content);
			content.release();

			if (reader.isEnd()) {
				String resultStr = new String(reader.readFull());
				System.out.println("Server said:" + resultStr);
				
				ctx.close();
			}
		}
	}

}

5、ByteBufToBytes 读取NIO的工具类，可以一次性把ByteBuf的数据读取出来，也可以把多次ByteBuf中的数据统一读取出来。

package com.guowl.utils;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;

public class ByteBufToBytes {
	private ByteBuf	temp;

	private boolean	end	= true;

	public ByteBufToBytes(int length) {
		temp = Unpooled.buffer(length);
	}

	public void reading(ByteBuf datas) {
		datas.readBytes(temp, datas.readableBytes());
		if (this.temp.writableBytes() != 0) {
			end = false;
		} else {
			end = true;
		}
	}

	public boolean isEnd() {
		return end;
	}

	public byte[] readFull() {
		if (end) {
			byte[] contentByte = new byte[this.temp.readableBytes()];
			this.temp.readBytes(contentByte);
			this.temp.release();
			return contentByte;
		} else {
			return null;
		}
	}

	public byte[] read(ByteBuf datas) {
		byte[] bytes = new byte[datas.readableBytes()];
		datas.readBytes(bytes);
		return bytes;
	}
}

注意事项：

1、可以通过在Netty的Chanel中发送HttpRequest对象，完成发送http请求的要求，同时可以对HttpHeader进行设置。

2、可以通过HttpResponse发送http响应，同时可以对HttpHeader进行设置。

3、上面涉及到的http对象都是Netty自己封装的，不是标准的。

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